1. Field of the Invention
The present invention relates to a communication device and a terminal, and in particular to a communication device and a terminal which perform wireless communication by use of EUTRAN.
2. Description of the Related Art
Currently, EUTRAN (Evolved UTRAN: Evolved UMTS Terrestrial Radio Access Network) is under study for a system in the next generation ahead of 3GPP (3rd Generation Partnership Project), and a scheme in which a single carrier is used in the uplink is in the course of being adopted. Specifically, the entire transmission bandwidth of the uplink is divided into a plurality of sub-bands, and each sub-band is occupied by a single carrier. Each single-carrier signal is assumed to be generated by FFT/IFFT (fast Fourier transformation/inverse fast Fourier transformation) processing, so that each single-carrier signal is composed of a plurality of subcarriers. Each terminal transmits data through one of the sub-bands in the uplink. However, basically the base station determines which one of the sub-bands each terminal should use.
The sub-band to be used is changed according to variations in the communication quality (wireless link quality). It is necessary for each terminal to have the base station determine which one of the sub-bands the terminal can use, and how long the terminal can use the sub-band, before uplink data transmission. (That is, wireless resource assignment is necessary.) Therefore, each terminal transmits to the base station a request signal for wireless resource assignment in accordance with a random access protocol (for example, the Slotted ALOHA protocol), or a reservation-type transmission protocol using a wireless resource assigned to the terminal by the base station.
However, each terminal transmits a pilot (reference signal) through only the sub-band to be used in data transmission, instead of the entire transmission bandwidth. Then, the base station evaluates the communication quality of the sub-band used in the transmission of the reference signal, on the basis of the reference signal. However, since each terminal does not transmit the reference signal through the entire transmission bandwidth, it is impossible to assign a sub-band which has communication quality suitable for each terminal. The base station can merely recognize the degree of the communication quality of the sub-band for each terminal. Therefore, it is impossible to perform frequency scheduling in the uplink.
Conventionally, some methods and devices for assigning channels in a mobile communication system using a plurality of different multiple access techniques have been proposed, where the methods and devices require neither complex algorithm nor massive calculation, and wireless frequencies can be effectively utilized. (See, for example, Japanese Unexamined Patent Publication No. 2002-218526).
As explained above, assignment of an uplink sub-band having satisfactory communication quality to each terminal is conventionally impossible.